Here’s a small tip when working with Core Data. If you have some convenience methods or other behavior you’d like to add to your managed object, please do so by creating a category for your managed object class. This way you can regenerate your managed object classes without losing your precious methods.
Example:
The header file of the generated managed object class:

The category that extends the functionality of the managed object:

take care,
phil.
For those who struggle with workspaces, multiple projects and shared static libraries, read this blog post by Jonah Williams.
“Programming as an intellectual activity is the only art form that allows you to create interactive art. You can create projects that other people can play with, and you can talk to them indirectly. No other art form is quite this interactive. Movies flow to the audience in one direction. Paintings do not move. Code goes both ways.”
Learn Python The Hard Way, Zed A. Shaw.
It is not the only art form to create interactive art, but who cares or dares to disagree: Zed A. Shaw is Chuck Norris (for programmers, Motherfucker!)